The present invention relates to devices for machining eyeglass lenses and, more particularly, to an apparatus for generating lens surfaces on a plurality of lens blanks in a single operation, whereby a cutting tool traverses the lens surface of each lens blank in a raster-like pattern according to one or more lens prescriptions.
A common procedure used to make a lens for a pair of prescription eyeglasses employs a lens blank of glass or plastic having two major lens surfaces. Generally, one of the major surfaces is pre-finished and the other surface requires cutting and polishing operations performed on it to satisfy a given lens prescription for a particular eyeglass wearer. The lens blank is usually mounted in a lens surface generating apparatus that incorporates a cutting tool for engaging the major surface of the lens blank to be cut and polished. The cutting tool is typically moved along multiple axes in response to commands issued from a controller in accordance with data representing the prescription for the lens.
The cutting tool used to generate the convex or concave contours of the lens surface typically has a spherical cutting end or tip that rotates as it moves over the surface of the lens blank. This type of cutting tool is commonly referred to as a ball mill. During a lens surface generating operation, the ball mill is typically moved over the surface of the lens blank in a spiral pattern, beginning at the periphery of the lens blank and culminating at the blank""s center. Lathe-type devices with a single point tool are also known.
One problem associated with the spiral machining is that the center of the lens includes an abnormality that requires a secondary operation to remove the abnormality.
Another difficulty encountered with generating a lens surface in this manner is that known lens surface generating apparatus generally accommodate a single lens blank, making the process for generating more than one lens time consuming and expensive.
Based on the foregoing, it is desirable to provide a lens surface generating apparatus that overcomes the above-described drawbacks of the prior art.
It is an object of the present invention to provide an improved apparatus and method for generating a lens surface.
It is another object of the present invention to provide a lens surface generating apparatus that can generate multiple lenses in a single operation each according to a different prescription.
According to the present invention, an apparatus for simultaneously machining a plurality of lens blanks to provide a lens surface on each blank corresponding to a selected lens prescription includes a tool support assembly and a lens blank assembly. The tool support assembly movably supports at least one tool. The lens blank support assembly includes a plurality of lens blank retainers for supporting a plurality of lens blanks. The tool support assembly and the lens support assembly move relative to each other such that the tool alternatingly engages each of the plurality of lens blanks for machining an individual lens prescription in a raster-like manner on each of the plurality of lens blanks.
In the preferred embodiment of the present invention, the tool support assembly includes a cutting tool rotatable about an axis substantially parallel to a Z-axis and movable in an X-axis direction in accordance with the individual lens prescription for each lens blank. The lens support assembly includes a flywheel with a plurality of lens blanks secured thereto. The flywheel is movable in the Z-axis direction and rotatable about Z-axis such that the cutting tool engages each lens blank individually for machining proper prescription thereon.
According to a feature of the present invention, a finishing tool is also supported by the tool support assembly to finish the polishing of each of the lens blanks.
According to another embodiment of the present invention, at least one tool is disposed on a flywheel that is rotatable about a Z-axis and movable in the Z-axis direction and a plurality of lens blanks are supported by a frame. Each lens blank is movable by an actuator in an X-axis direction in accordance with the individual lens prescription into engagement with the tool for machining proper prescription onto each of the lenses.
The apparatus of the present invention allowing raster-like machining of multiple lenses results in a lens that does not include a central abnormality, thereby yielding a better final product.
One advantage of the present invention is that multiple lenses are generated simultaneously with each lens blank being machined according to its individual prescription.
The foregoing and other advantages of the present invention become more apparent in light of the following detailed description of the exemplary embodiments thereof, as illustrated in the accompanying drawings.